Coagulation Activity of the Seed Extract from Zygia cauliflora (WILLD.) KILLIP applied in Water Treatment

Abstract

The use of natural coagulants is a promising alternative to replace or assist chemical coagulants due to its numerous advantages. This paper evaluates the effectiveness of a natural coagulant in water treatment. The coagulant was extracted from the Zygia cauliflora (Willd.) Killip seed in saline solutions and defatted using 95% ethanol. The tests were conducted using different concentrations of the coagulant (0.1, 0.5, 1.0, 2.0, 3.0, and 4.0 g L^-1) and of NaCl (0.0 M, 1.0 M, and 5.0 M). The results showed that the use of 2 g L^-1 of coagulant and 1.0 M of the salt achieved an effectiveness of 20% and 70%, respectively, of color and turbidity removal. The analysis showed an effectiveness of 70% and 30%, respectively, when removing the UV₂₅₄ compound and DOM (dissolved organic matter). The mechanism for turbidity removal by the coagulants prepared with aqueous solution and with saline solution at 1.0 M of NaCl is supposed to be adsorption and charge neutralization, respectively, following the Freundlich and Langmuir models. However, the coagulant prepared with saline solution at 5.0 M of NaCl tends to form a netlike structure followed by turbidity removal through a sweep coagulation mechanism. Future papers should therefore focus on the use of Zygia cauliflora (Willd.) Killip as an alternative for replacement or use as an auxiliary chemical coagulant.